Field of the Invention
The present invention relates to an internal combustion engine control apparatus and particularly to an internal combustion engine control apparatus that makes it possible to determine whether an internal combustion engine is in a steady-operation mode or in a transient-operation mode and that can perform appropriate control even when the internal combustion engine is in the transient-operation mode.
Description of the Related Art
To date, it has been known that the operation modes of an internal combustion engine include a steady-operation mode and a transient-operation mode; by changing a control method or a control constant for the internal combustion engine in accordance with the operation mode, control suitable for the operation mode is performed. Here, the steady-operation mode of an internal combustion engine denotes a case where the internal combustion engine is operated with an approximately constant rotation speed and approximately constant output. In the steady-operation mode, by setting to be large the filter coefficient for filtering processing of the inputs from sensors, for example, an air flow sensor, an intake pipe inner pressure sensor, a knock sensor, and the like, i.e., by setting the cut-off frequency to be low, fluctuation in the intake amount measurement is reduced so that fluctuation in the control amounts of ignition timing control and fuel injection control is suppressed, and by reducing fluctuation in the background level (referred to as a BGL, hereinafter), which is the average value of the vibration level of a knock sensor signal in knock control, fluctuation in the knock determination threshold value level is suppressed. Accordingly, there is obtained a stable operation mode with less torque fluctuation; in the case where a knock occurs, control is performed in such a way that the knock is accurately detected, and retarding correction is applied to the ignition timing so that the knock is suppressed.
The transient-operation mode of an internal combustion engine denotes a case where the internal combustion engine is operated in a transient mode where the rotation speed and the output of the internal combustion engine are increasing or decreasing. In the case where the transient-operation mode is detected, by setting to be small the foregoing filter coefficient of filtering processing of inputs from sensors, i.e., by setting the cut-off frequency to be high, the response speed of the intake amount measurement is raised so that there is raised the tracking capability for the control amounts in the ignition timing control and the fuel injection control and hence deterioration in the exhaust gas is suppressed. In the case of rapid acceleration or the like, there exists a case where in fuel injection control, control is performed in such a way as to create the feeling of acceleration, by raising the torque through transient amount-increasing correction or a case where even in ignition-timing correction, several-stroke transient retard correction is implemented so as to suppress a transient knock, and then by raising the response speed of the BGL in knock control, the threshold value level is controlled with a high tracking capability so that control is performed in such a way as to suppress torque from being decreased by erroneous retarding correction.
As an example of method of performing switching between control in the steady-operation mode and control in the transient-operation mode, Patent Document 1 proposes a method in which in the case of transient-operation mode with knock control, a knock determination threshold value is corrected so that there is prevented an erroneous knock retarding correction due to rapid change in the level of a knock sensor signal. Patent Document 2 proposes a method in which an acceleration/deceleration mode value is calculated from the calculation value obtained by applying filtering to a loaded-mode value so that the fuel injection amount is corrected. Furthermore, Patent Document 3 proposes a method in which based on the rotation speed of an internal combustion engine, the throttle opening degree, and the displacement angle in the intake valve timing, there is calculated an estimated value for a change, in inner-cylinder contained air amount, caused by a change of the intake valve timing in the transient-operation mode, so that the inner-cylinder contained air amount is accurately calculated from the calculation value obtained by applying filtering to the foregoing estimated value.
Patent Document 4 discloses the fact that a load information value such as filling efficiency rises in such a manner as a first-order lag response, as the throttle opening degree changes (described later). Patent Document 5 discloses that when an internal combustion engine is operated in the transient-operation mode, filter coefficients are switched (described later).